Compared with well-developed free space polarization converters, polarization conversion between TE and TM modes in the waveguide is generally considered to be caused by shape birefringence, like curvature, morphology...Compared with well-developed free space polarization converters, polarization conversion between TE and TM modes in the waveguide is generally considered to be caused by shape birefringence, like curvature, morphology of waveguide cross section and scattering. Here, we study the polarization conversion mechanism in 1-THz-FSR X-cut lithium niobate microrings with multiple-resonance condition, that is the conversion can be implemented by birefringence of waveguides,which will also introduce an avoided-mode crossing. In the experiment, we find that this mode crossing results in severe suppression of one sideband in local nondegenerate four-wave mixing and disrupts the cascaded four-wave mixing on this side. Simultaneously, we propose one two-dimensional method to simulate the eigenmodes(TE and TM) in X-cut microrings, and the mode crossing point. This work will provide one approach to the design of polarization converters and simulation for monolithic photonics integrated circuits, and may be helpful to the studies of missed temporal dissipative soliton formation in X-cut lithium niobate rings.展开更多
Simultaneous broadband absorption and polarization conversion are crucial in many practical applications,especially in terahertz communications.Thus,actively tunable metamaterial systems can exploit the graphene-based...Simultaneous broadband absorption and polarization conversion are crucial in many practical applications,especially in terahertz communications.Thus,actively tunable metamaterial systems can exploit the graphene-based nanomaterials derived from renewable resources because of the flexible surface conductivity and selective permeability of the nanomaterials at terahertz frequencies.In this paper,we propose a graphene-based active tunable bifunctional metasurface for dynamic terahertz absorption and polarization conversion.The graphene ring presents a certain opening angle(A)along the diagonal of the xoy plane.When A=0°,the proposed metasurface behaves as a broadband absorber.Numerical results show the feasibility of achieving this polarization-insensitive absorber with nearly 100%absorptance,and the bandwidth of its 90%absorptance is 1.22 THz under normal incidence.Alternatively,when A=40°after optimization,the proposed metasurface serves as a broadband polarization convertor,resulting in robust broadband polarization conversion ratio(PCR)curves with a bandwidth surpassing 0.5 THz in the reflection spectrum.To tune the PCR response or the broad absorption spectrum of graphene,we change the Fermi energy of graphene dynamically from 0 to 0.9 eV.Furthermore,both the broadband absorption and the linear polarization conversion spectra of the proposed metasurface exhibit insensitivity to the incident angle,allowing large incident angles within 40°under high-performance operating conditions.To demonstrate the physical process,we present the impedance matching theory and measure electric field distributions.This architecture in the THz frequency range has several applications,such as in modulators,sensors,stealth,and optoelectronic switches.THz wave polarization and beam steering also have broad application prospects in the field of intelligent systems.展开更多
The terahertz(THz)resonance,chirality,and polarization conversion properties of a double-layer chiral metasurface have been experimentally investigated by THz time domain spectroscopy system and polarization detection...The terahertz(THz)resonance,chirality,and polarization conversion properties of a double-layer chiral metasurface have been experimentally investigated by THz time domain spectroscopy system and polarization detection method.The special symmetric geometry of each unit cell with its adjacent cells makes a strong chiral electromagnetic response in this metasurface,which leads to a strong polarization conversion effect.Moreover,compared with the traditional THz transmission resonance sensing for film thickness,the polarization sensing characterized by polarization elliptical angle(PEA)and polarization rotation angle(PRA)shows a better Q factor and figure of merit(FoM).The results show that the Q factors of the PEA and PRA reach 43.8 and 49.1 when the interval film is 20µm,while the Q factor of THz resonance sensing is only 10.6.And these PEA and PRA can play a complementary role to obtain a double-parameter sensing method with a higher FoM,over 4 times than that of resonance sensing.This chiral metasurface and its polarization sensing method provide new ideas for the development of high-efficiency THz polarization manipulation,and open a window to the high sensitive sensing by using THz polarization spectroscopy.展开更多
We present a transmission-type polarization conversion metamaterial(PCM)whose functions can be dynamically switched among the linear-to-circular(LTC)and linear-to-linear(LTL)polarization conversions.The proposed PCM c...We present a transmission-type polarization conversion metamaterial(PCM)whose functions can be dynamically switched among the linear-to-circular(LTC)and linear-to-linear(LTL)polarization conversions.The proposed PCM consists of a grating,a polarization conversion surface and a reconfigurable polarization selective surface incorporated with PIN diodes.By changing the states of diodes,the PCM can achieve the reconfigurable manipulations for incident waves.The Fabry-Pérot(F-P)resonances excited by the PCM contribute to the polarization conversions,as is illustrated.Moreover,through establishing the F-P-like cavity model and analyzing the electric field components of the transmitted waves,the conditions for realizing LTC polarization conversion are revealed,which can guide the construction of PCM.The prototype of PCM is fabricated and measured,which can achieve LTC and LTL polarization conversions within 3.31-3.56 GHz and 2.76-4.24 GHz,respectively,the polarization conversion ratios of two functions are higher than 0.95.The measurement results are in agreement with the simulation data.展开更多
We propose a broadband perfect polarization conversion metasurface composed of copper sheet-backed asymmetric double spilt ring resonator(DSRR). The broadband perfect polarization convertibility results from metalli...We propose a broadband perfect polarization conversion metasurface composed of copper sheet-backed asymmetric double spilt ring resonator(DSRR). The broadband perfect polarization convertibility results from metallic ground and multiple plasmon resonances of the DSRR. Physics of plasmon resonances are governed by the electric and magnetic resonances. Both the simulation and measured results show that the polarization conversion ratio(PCR) is higher than 99%for both x- and y-polarized normally incident EM waves and the fractional bandwidth is about 34.5%. The metasurface possesses the merits of high PCR and broad bandwidth, and thus has great application values in novel polarization-control devices.展开更多
Polarization conversion is a very important electromagnetic wave manipulation method.In this paper,we investigate a high-efficiency linear-to-circular polarization and cross-polarization converter by utilizing coding ...Polarization conversion is a very important electromagnetic wave manipulation method.In this paper,we investigate a high-efficiency linear-to-circular polarization and cross-polarization converter by utilizing coding metasurface.The coding particle consists of top layer metal pattern and bottom metal plate sandwiched with square F4B dielectric,which can manipulate the linear-to-circular polarization and cross-polarization converter of the reflected wave simultaneously.In the terahertz frequency range of 1.0 THz-2.0 THz,the reflection magnitudes reach approximately 90%and the axial ratio is less than 3 dB.The proposed polarization converter may lead to advances in a variety of applications such as security,microscopy,information processing,stealth technology,and data storage.展开更多
An ultra-wideband and high-efficiency reflective linear-to-circular polarization conversion metasurface is proposed. The proposed metasurface is composed of a square array of a corner-truncated square patch printed on...An ultra-wideband and high-efficiency reflective linear-to-circular polarization conversion metasurface is proposed. The proposed metasurface is composed of a square array of a corner-truncated square patch printed on grounded dielectric substrate and covered with a dielectric layer, which is an orthotropic anisotropic structure with a pair of mutually perpendicular symmetric axes u and v along the directions with the tilt angles of ±45° with respect to the vertical y axis. When the u- and v-polarized waves are incident on the proposed metasurface, the phase difference between the two reflection coefficients is close to –90° in an ultra-wide frequency band, so it can realize high-efficiency and ultra-wideband LTC polarization conversion under both x- and y-polarized incidences in this band. The proposed polarization conversion metasurface is simulated and measured. Both the simulated and measured results show that the axial ratio (AR) of the reflected wave is kept below 3 dB in the ultra-wide frequency band of 5.87 GHz–21.13 GHz, which is corresponding to a relative bandwidth of 113%;moreover, the polarization conversion rate (PCR) can be kept larger than 99% in a frequency range of 8.08 GHz–20.92 GHz.展开更多
Resonant responses of metasurface enable effective control over the polarization properties of lights. In this paper,we demonstrate a double-rod metasurface for broadband polarization conversion in the mid-infrared re...Resonant responses of metasurface enable effective control over the polarization properties of lights. In this paper,we demonstrate a double-rod metasurface for broadband polarization conversion in the mid-infrared region. The metasurface consists of a metallic double-rod array separated from a reflecting ground plane by a film of zinc selenide. By superimposing three localized resonances, cross polarization conversion is achieved over a bandwidth of 16.9 THz around the central frequency at 34.6 THz with conversion efficiency exceeding 70%. The polarization conversion performance is in qualitative agreement with simulation. The surface current distributions and electric field profiles of the resonant modes are discussed to analyze the underlying physical mechanism. Our demonstrated broadband polarization conversion has potential applications in the area of mid-infrared spectroscopy, communication, and sensing.展开更多
The terahertz technology has attracted considerable attention because of its potential applications in various fields.However,the research of functional devices,including polarization converters,remains a major demand...The terahertz technology has attracted considerable attention because of its potential applications in various fields.However,the research of functional devices,including polarization converters,remains a major demand for practical applications.In this work,a reflective dual-functional terahertz metadevice is presented,which combines two different polarization conversions through using a switchable metasurface.Different functions can be achieved because of the insulator-to-metal transition of vanadium dioxide(VO_(2)).At room temperature,the metadevice can be regarded as a linear-to-linear polarization convertor containing a gold circular split-ring resonator(CSRR),first polyimide(PI)spacer,continuous VO_(2) film,second PI spacer,and gold substrate.The converter possesses a polarization conversion ratio higher than 0.9 and a bandwidth ratio of 81%in a range from 0.912 THz to 2.146 THz.When the temperature is above the insulator-to-metal transition temperature(approximately 68℃)and VO_(2) becomes a metal,the metasurface transforms into a wideband linear-to-circular polarization converter composed of the gold CSRR,first PI layer,and continuous VO_(2) film.The ellipticity is close to-1,while the axis ratio is lower than 3 dB in a range of 1.07 THz-1.67 THz.The metadevice also achieves a large angle tolerance and large manufacturing tolerance.展开更多
We proposed a sandwich structure to realize broadband asymmetric transmission(AT) for both linearly and circularly polarized waves in the near infrared spectral region. The structure composes of a silica substrate and...We proposed a sandwich structure to realize broadband asymmetric transmission(AT) for both linearly and circularly polarized waves in the near infrared spectral region. The structure composes of a silica substrate and two sand-clock-like gold layers on the opposite sides of the substrate. Due to the surface plasmons of gold, the structure shows that the AT parameters of linearly and circularly polarized waves can reach 0.436 and 0.403, respectively. Meanwhile, a broadband property is presented for the AT parameter is over 0.3 between 320 THz and 340 THz. The structure realizes a diode-like AT for linearly wave in forward and circularly wave in backward, respectively. The magnetic dipoles excited by current in the two gold layers contribute to the broadband AT. The current density in top and bottom metallic layers illustrates the mechanism of the polarization conversion for broadband AT in detail.展开更多
A switchable terahertz(THz)polarization converter based on vanadium dioxide(VO_(2)) metamaterial is proposed.It is a 5-layer structure which containing metal split-ring-resonator(SRR),the first polyimide(PI)spacer,VO_...A switchable terahertz(THz)polarization converter based on vanadium dioxide(VO_(2)) metamaterial is proposed.It is a 5-layer structure which containing metal split-ring-resonator(SRR),the first polyimide(PI)spacer,VO_(2) film,the second PI spacer,and metal grating.It is an array structure and the period in x and y directions is 100μm.The performance is simulated by using finite integration technology.The simulation results show that,when the VO_(2) is in insulating state,the device is a transmission polarization converter.The cross-linear polarization conversion can be realized in a broadband of0.70 THz,and the polarization conversion rate(PCR)is higher than 99%.Under thermal stimulus,the VO_(2) changes from insulating state to metallic state,and the device is a reflective polarization converter.The linear-to-circular polarization conversion can be successfully realized in a broadband of 0.50 THz,and the PCR is higher than 88%.展开更多
We propose the design of anisotropic metamaterials with cascading meta-atoms.Each meta-atom array behaves as an impedance-tuned interface and dramatically modifies the complex reflection and transmission coefficients....We propose the design of anisotropic metamaterials with cascading meta-atoms.Each meta-atom array behaves as an impedance-tuned interface and dramatically modifies the complex reflection and transmission coefficients.By engineering the frequency-dependent impedances,the reflection phase difference along the two axes of anisotropic metamaterials approximates to a constant in a wide range.We numerically demonstrate the proposed anisotropic metamaterials can accomplish achromatic polarization transformation from 0.5 THz to 3.1 THz.The polarization conversion ratio is higher than 80%,which exhibits excellent agreements with the theoretical calculation.Such design is scalable to other bands and can provide helpful guidance in broadband devices design.展开更多
In this paper, we propose a three-layered chiral metamaterial (CMM) that exhibits an asymmetric transmission effect for linearly polarized waves along forwardly and backwardly propagating in the microwave region, whic...In this paper, we propose a three-layered chiral metamaterial (CMM) that exhibits an asymmetric transmission effect for linearly polarized waves along forwardly and backwardly propagating in the microwave region, which not only realizes the asymmetric transmission effect of multi-frequency points for linearly polarized wave in microwave band, but also breaks through the limitation of single transformation from linear polarization to linear polarization. Numerical simulation results indicate that incident wave for linearly polarized waves will be converted and transmitted as a circularly polarized wave along the forward direction at 8.31 GHz. Moreover, the asymmetric transmission (AT) parameter Δ achieves 0.8 around 12 GHz, proving the existence of strong polarization conversion and diode-like function. The proposed CMM shows great potential applications in high performance linear polarization convertor and isolator in microwave frequency.展开更多
In this paper,we propose an ultrabroadband chiral metasurface(CMS)composed of S-shaped resonator structures situated between two twisted subwavelength gratings and dielectric substrate.This innovative structure enable...In this paper,we propose an ultrabroadband chiral metasurface(CMS)composed of S-shaped resonator structures situated between two twisted subwavelength gratings and dielectric substrate.This innovative structure enables ultrabroadband and high-efficiency linear polarization(LP)conversion,as well as asymmetric transmission(AT)effect in the microwave region.The enhanced interference effect of the Fabry-Perot-like resonance cavity greatly expands the bandwidth and efficiency of LP conversion and AT effect.Through numerical simulations,it has been revealed that the cross-polarization transmission coefficients for normal forward(-z)and backward(+z)incidence exceed 0.8 in the frequency range of 4.13 to 17.34 GHz,accompanied by a polarization conversion ratio of over 99%.Furthermore,our microwave experimental results validate the consistency among simulation,theory,and measurement.Additionally,we elucidate the distinct characteristics of ultrabroadband LP conversion and significant AT effect through analysis of polarization azimuth rotation and ellipticity angles,total transmittance,AT coefficient,and electric field distribution.The proposed CMS structure shows excellent polarization conversion properties via AT effect and has potential applications in areas such as radar,remote sensing,and satellite communication.展开更多
We experimentally investigate the linear polarization conversion for terahertz(THz)waves in liquid crystal(LC)integrated metamaterials,which consist of an LC layer sandwiched by two orthogonally arranged sub-wavelengt...We experimentally investigate the linear polarization conversion for terahertz(THz)waves in liquid crystal(LC)integrated metamaterials,which consist of an LC layer sandwiched by two orthogonally arranged sub-wavelength metal gratings.A Fabry-Perot-like cavity is well constructed by the front and rear gratings,and it shows a strong local resonance mechanism,which greatly enhances the polarization conversion efficiency.Most importantly,the Fabry-Perot-like resonance can be actively tuned by modulating the refractive index of the middle LC layer under the external field.As a result,the integrated metamaterial achieves multi-band tunable linear polarization conversion.展开更多
Phase-modulated metasurfaces that can implement the independent manipulation of co-and cross-polarized output waves under circularly polarized[CP]incidence have been proposed.With this,we introduce one particular meta...Phase-modulated metasurfaces that can implement the independent manipulation of co-and cross-polarized output waves under circularly polarized[CP]incidence have been proposed.With this,we introduce one particular metasurface composed of meta-atoms with a phase difference of 2π/3 to generate specific elliptically polarized waves under various polarized incidences.Furthermore,a metasurface composed of these above meta-atoms and the meta-atoms with a phase difference of π/3 arranged in a certain rule can realize polarization conversion function between linearly polarized and CP states.The designs shed new light on multifarious optical devices and may further promote the development of metasurface polarization optics.展开更多
In this Letter, we demonstrate a linear polarization conversion of transmitted terahertz wave with double-layer meta-grating surfaces, which integrated the frequency selectivity of a split ring resonator metasurface a...In this Letter, we demonstrate a linear polarization conversion of transmitted terahertz wave with double-layer meta-grating surfaces, which integrated the frequency selectivity of a split ring resonator metasurface and the polarization selectivity of a metallic grating surface. Since the double-layer can reduce the loss, and the Fabry- Perot like resonant effect between the two layers can improve the conversion efficiency, this converter can rotate the incident y-polarized terahertz wave into an x-polarized transmitted wave with relatively low loss and high efficiency. Experimental results show that an average conversion efficiency exceeding 75% from 0.25 to 0.65 THz with the highest efficiency of 90% at 0.43 THz with onlv -2 dB loss has been achieved.展开更多
This study proposes a bi-layer windmill-shaped metamaterial that consists of resonators, with similar shapes, on both sides of a dielectric substrate. In this study, the second layer is rotated clockwise around the su...This study proposes a bi-layer windmill-shaped metamaterial that consists of resonators, with similar shapes, on both sides of a dielectric substrate. In this study, the second layer is rotated clockwise around the substrate normal at 90°and thereafter flipped in the first layer. Due to the introduction of a windmill-like shape, the resonant structures result in new resonant modes and thus can achieve multi-band high-efficiency cross-polarization conversions and asymmetric transmissions(ATs) for a linearly polarized incident plane wave with a maximum asymmetric parameter of 0.72. Depending on the geometric parameters of our windmill-shaped structures, the AT effects can be flexibly modulated in a broad multiband from 160 THz to 400 THz, which has not been reported in previous studies. These outstanding AT effects provide potential applications in optical diodes, polarization control switches, and other nano-devices.展开更多
A three-dimensional chiral metamaterial with four-fold rotational symmetry is designed, and its optical properties are investigated by numerical simulations. The results show that this chiral metamaterial has the foll...A three-dimensional chiral metamaterial with four-fold rotational symmetry is designed, and its optical properties are investigated by numerical simulations. The results show that this chiral metamaterial has the following features:high polarization conversion, perfect circular dichroism, and asymmetric transmission of circularly polarized light. A comparison of the results of chiral metamaterials without and with weak coupling between the constituent nanostructures enables us to confirm that the optical properties of our proposed nanostructure are closely related to the coupling between the single nanoparticles. This means that the coupling between nanoparticles can enhance the polarization conversion, circular dichroism, and asymmetric transmission. Due to the excellent optical properties, our metamaterial might have potential applications in the development of future multi-functional optical devices.展开更多
Polarization,a fundamental behavior of electromagnetic waves,holds immense potential across diverse domains such as environmental monitoring,biomedicine,and ocean exploration.However,achieving efcient modulation of te...Polarization,a fundamental behavior of electromagnetic waves,holds immense potential across diverse domains such as environmental monitoring,biomedicine,and ocean exploration.However,achieving efcient modulation of terahertz waves with wide operational bandwidth poses signifcant challenges.Here,we introduce an all-silicon polarization converter designed specifcally to operate in the terahertz range of the electromagnetic spectrum.Simulation results demonstrate that the average conversion efciency of cross-linear waves exceeds 80%across a wide frequency range spanning from 1.00 to 2.32 THz,with the highest conversion efciency peaking at an impressive 99.97%.Additionally,our proposed structure facilitates linear-to-circular polarization conversion with an ellipticity of 1 at 0.85 THz.Furthermore,by rotating the crossshaped microstructure,active control over arbitrary polarization states can be achieved.To summarize,the proposed structure ofers remarkable fexibility and ease of integration,providing a reliable and practical solution for achieving broadband and efcient polarization conversion of terahertz waves.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 12274462 and 11674396)the Department of Science and Technology of Hunan Province of China (Grant Nos. 2017RS3039 and 2018JJ1033)the Hunan Provincial Innovation Foundation for Postgraduate of China (Grant No. QL20210006)。
文摘Compared with well-developed free space polarization converters, polarization conversion between TE and TM modes in the waveguide is generally considered to be caused by shape birefringence, like curvature, morphology of waveguide cross section and scattering. Here, we study the polarization conversion mechanism in 1-THz-FSR X-cut lithium niobate microrings with multiple-resonance condition, that is the conversion can be implemented by birefringence of waveguides,which will also introduce an avoided-mode crossing. In the experiment, we find that this mode crossing results in severe suppression of one sideband in local nondegenerate four-wave mixing and disrupts the cascaded four-wave mixing on this side. Simultaneously, we propose one two-dimensional method to simulate the eigenmodes(TE and TM) in X-cut microrings, and the mode crossing point. This work will provide one approach to the design of polarization converters and simulation for monolithic photonics integrated circuits, and may be helpful to the studies of missed temporal dissipative soliton formation in X-cut lithium niobate rings.
基金supported by the High Level Talent Project of Basic and Applied Basic Research(Natural Science)of Hainan Province in 2019(No.2019RC158)by the Project of the Education Department of Hainan Province(No.Hnky2020ZD-2),all support is gratefully acknowledged.
文摘Simultaneous broadband absorption and polarization conversion are crucial in many practical applications,especially in terahertz communications.Thus,actively tunable metamaterial systems can exploit the graphene-based nanomaterials derived from renewable resources because of the flexible surface conductivity and selective permeability of the nanomaterials at terahertz frequencies.In this paper,we propose a graphene-based active tunable bifunctional metasurface for dynamic terahertz absorption and polarization conversion.The graphene ring presents a certain opening angle(A)along the diagonal of the xoy plane.When A=0°,the proposed metasurface behaves as a broadband absorber.Numerical results show the feasibility of achieving this polarization-insensitive absorber with nearly 100%absorptance,and the bandwidth of its 90%absorptance is 1.22 THz under normal incidence.Alternatively,when A=40°after optimization,the proposed metasurface serves as a broadband polarization convertor,resulting in robust broadband polarization conversion ratio(PCR)curves with a bandwidth surpassing 0.5 THz in the reflection spectrum.To tune the PCR response or the broad absorption spectrum of graphene,we change the Fermi energy of graphene dynamically from 0 to 0.9 eV.Furthermore,both the broadband absorption and the linear polarization conversion spectra of the proposed metasurface exhibit insensitivity to the incident angle,allowing large incident angles within 40°under high-performance operating conditions.To demonstrate the physical process,we present the impedance matching theory and measure electric field distributions.This architecture in the THz frequency range has several applications,such as in modulators,sensors,stealth,and optoelectronic switches.THz wave polarization and beam steering also have broad application prospects in the field of intelligent systems.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFA0701000)the National Natural Science Foundation of China(Grant Nos.61971242,61831012,and 61671491)+1 种基金the Natural Science Foundation of Tianjin City,China(Grant No.19JCYBJC16600)the Young Elite Scientists Sponsorship Program by Tianjin,China(Grant No.TJSQNTJ-2017-12).
文摘The terahertz(THz)resonance,chirality,and polarization conversion properties of a double-layer chiral metasurface have been experimentally investigated by THz time domain spectroscopy system and polarization detection method.The special symmetric geometry of each unit cell with its adjacent cells makes a strong chiral electromagnetic response in this metasurface,which leads to a strong polarization conversion effect.Moreover,compared with the traditional THz transmission resonance sensing for film thickness,the polarization sensing characterized by polarization elliptical angle(PEA)and polarization rotation angle(PRA)shows a better Q factor and figure of merit(FoM).The results show that the Q factors of the PEA and PRA reach 43.8 and 49.1 when the interval film is 20µm,while the Q factor of THz resonance sensing is only 10.6.And these PEA and PRA can play a complementary role to obtain a double-parameter sensing method with a higher FoM,over 4 times than that of resonance sensing.This chiral metasurface and its polarization sensing method provide new ideas for the development of high-efficiency THz polarization manipulation,and open a window to the high sensitive sensing by using THz polarization spectroscopy.
基金Project supported by the Fundamental Research Funds for Central Universities(Grant No.2682020GF03)
文摘We present a transmission-type polarization conversion metamaterial(PCM)whose functions can be dynamically switched among the linear-to-circular(LTC)and linear-to-linear(LTL)polarization conversions.The proposed PCM consists of a grating,a polarization conversion surface and a reconfigurable polarization selective surface incorporated with PIN diodes.By changing the states of diodes,the PCM can achieve the reconfigurable manipulations for incident waves.The Fabry-Pérot(F-P)resonances excited by the PCM contribute to the polarization conversions,as is illustrated.Moreover,through establishing the F-P-like cavity model and analyzing the electric field components of the transmitted waves,the conditions for realizing LTC polarization conversion are revealed,which can guide the construction of PCM.The prototype of PCM is fabricated and measured,which can achieve LTC and LTL polarization conversions within 3.31-3.56 GHz and 2.76-4.24 GHz,respectively,the polarization conversion ratios of two functions are higher than 0.95.The measurement results are in agreement with the simulation data.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61331005,11204378,11274389,11304393,and 61302023)the National Science Foundation for Post-doctoral Scientists of China(Grant Nos.2013M532131 and 2013M532221)+1 种基金the Natural Science Foundation of Shaanxi Province,China(Grant No.2013JM6005)the Aviation Science Foundation of China(Grant Nos.20132796018 and 20123196015)
文摘We propose a broadband perfect polarization conversion metasurface composed of copper sheet-backed asymmetric double spilt ring resonator(DSRR). The broadband perfect polarization convertibility results from metallic ground and multiple plasmon resonances of the DSRR. Physics of plasmon resonances are governed by the electric and magnetic resonances. Both the simulation and measured results show that the polarization conversion ratio(PCR) is higher than 99%for both x- and y-polarized normally incident EM waves and the fractional bandwidth is about 34.5%. The metasurface possesses the merits of high PCR and broad bandwidth, and thus has great application values in novel polarization-control devices.
基金Project supported by the National Key Research and Development Program of China(Grant No.2016YFF0200306)the National Natural Science Foundation of China(Grant Nos.61871355 and 61831012).
文摘Polarization conversion is a very important electromagnetic wave manipulation method.In this paper,we investigate a high-efficiency linear-to-circular polarization and cross-polarization converter by utilizing coding metasurface.The coding particle consists of top layer metal pattern and bottom metal plate sandwiched with square F4B dielectric,which can manipulate the linear-to-circular polarization and cross-polarization converter of the reflected wave simultaneously.In the terahertz frequency range of 1.0 THz-2.0 THz,the reflection magnitudes reach approximately 90%and the axial ratio is less than 3 dB.The proposed polarization converter may lead to advances in a variety of applications such as security,microscopy,information processing,stealth technology,and data storage.
基金Project supported by the Natural Science Foundation of Shaanxi Province, China (Grant Nos. 2019JM-077 and 2018JM-6098)the Scientific Research Program Funded by Shaanxi Provincial Education Department (Grant No. 18JK1195)the Shaanxi Key Research and Development Project, China (Grant No. 2019GY-055).
文摘An ultra-wideband and high-efficiency reflective linear-to-circular polarization conversion metasurface is proposed. The proposed metasurface is composed of a square array of a corner-truncated square patch printed on grounded dielectric substrate and covered with a dielectric layer, which is an orthotropic anisotropic structure with a pair of mutually perpendicular symmetric axes u and v along the directions with the tilt angles of ±45° with respect to the vertical y axis. When the u- and v-polarized waves are incident on the proposed metasurface, the phase difference between the two reflection coefficients is close to –90° in an ultra-wide frequency band, so it can realize high-efficiency and ultra-wideband LTC polarization conversion under both x- and y-polarized incidences in this band. The proposed polarization conversion metasurface is simulated and measured. Both the simulated and measured results show that the axial ratio (AR) of the reflected wave is kept below 3 dB in the ultra-wide frequency band of 5.87 GHz–21.13 GHz, which is corresponding to a relative bandwidth of 113%;moreover, the polarization conversion rate (PCR) can be kept larger than 99% in a frequency range of 8.08 GHz–20.92 GHz.
基金Project supported by the National Natural Science Foundation of China(Grants Nos.61421002 and 61575036)the Chinese National 1000 Plan for Young Talentsthe Startup Funding from University of Electronic Science and Technology of China
文摘Resonant responses of metasurface enable effective control over the polarization properties of lights. In this paper,we demonstrate a double-rod metasurface for broadband polarization conversion in the mid-infrared region. The metasurface consists of a metallic double-rod array separated from a reflecting ground plane by a film of zinc selenide. By superimposing three localized resonances, cross polarization conversion is achieved over a bandwidth of 16.9 THz around the central frequency at 34.6 THz with conversion efficiency exceeding 70%. The polarization conversion performance is in qualitative agreement with simulation. The surface current distributions and electric field profiles of the resonant modes are discussed to analyze the underlying physical mechanism. Our demonstrated broadband polarization conversion has potential applications in the area of mid-infrared spectroscopy, communication, and sensing.
基金the National Natural Science Foundation of China(Grant No.62001444)the Natural Science Foundation of Zhejiang Province,China(Grant No.LQ20F010009)+1 种基金the Basic Public Welfare Research Project of Zhejiang Province,China(Grant No.LGF19F010003)the State Key Laboratory of Crystal Materials,Shandong University,China(Grant No.KF1909)。
文摘The terahertz technology has attracted considerable attention because of its potential applications in various fields.However,the research of functional devices,including polarization converters,remains a major demand for practical applications.In this work,a reflective dual-functional terahertz metadevice is presented,which combines two different polarization conversions through using a switchable metasurface.Different functions can be achieved because of the insulator-to-metal transition of vanadium dioxide(VO_(2)).At room temperature,the metadevice can be regarded as a linear-to-linear polarization convertor containing a gold circular split-ring resonator(CSRR),first polyimide(PI)spacer,continuous VO_(2) film,second PI spacer,and gold substrate.The converter possesses a polarization conversion ratio higher than 0.9 and a bandwidth ratio of 81%in a range from 0.912 THz to 2.146 THz.When the temperature is above the insulator-to-metal transition temperature(approximately 68℃)and VO_(2) becomes a metal,the metasurface transforms into a wideband linear-to-circular polarization converter composed of the gold CSRR,first PI layer,and continuous VO_(2) film.The ellipticity is close to-1,while the axis ratio is lower than 3 dB in a range of 1.07 THz-1.67 THz.The metadevice also achieves a large angle tolerance and large manufacturing tolerance.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11965009,61874036,61805053,and 61764001)the Natural Science Foundation of Guangxi Zhuang Autonomous Region,China(Grant Nos.2018JJA170010 and 2018GXNSFAA281193)the Innovation Project of GUET Graduate Education(Grant No.2020YCXS019)。
文摘We proposed a sandwich structure to realize broadband asymmetric transmission(AT) for both linearly and circularly polarized waves in the near infrared spectral region. The structure composes of a silica substrate and two sand-clock-like gold layers on the opposite sides of the substrate. Due to the surface plasmons of gold, the structure shows that the AT parameters of linearly and circularly polarized waves can reach 0.436 and 0.403, respectively. Meanwhile, a broadband property is presented for the AT parameter is over 0.3 between 320 THz and 340 THz. The structure realizes a diode-like AT for linearly wave in forward and circularly wave in backward, respectively. The magnetic dipoles excited by current in the two gold layers contribute to the broadband AT. The current density in top and bottom metallic layers illustrates the mechanism of the polarization conversion for broadband AT in detail.
基金supported in part by the National Natural Science Foundation of China(Grant Nos.62065005,61565004,11774288,and 62003107)the Natural Science Foundation of Guangxi Zhuang Autonomous Region,China(Grant Nos.2018GXNSFAA050043,2020GXNSFDA238019,2019JJB110033,and 2017GXNSFBA198029)+2 种基金the Innovation Project of Guangxi Graduate Education,China(Grant Nos.YCSW2021188,YCBZ2021071,and 2020YCXB04)the Foundation from Guangxi Key Laboratory of Automatic Detecting Technology and Instrument(Grant No.YQ21101)the Research and Development Project in Hunan Province,China(Grant No.2020SK2111)。
文摘A switchable terahertz(THz)polarization converter based on vanadium dioxide(VO_(2)) metamaterial is proposed.It is a 5-layer structure which containing metal split-ring-resonator(SRR),the first polyimide(PI)spacer,VO_(2) film,the second PI spacer,and metal grating.It is an array structure and the period in x and y directions is 100μm.The performance is simulated by using finite integration technology.The simulation results show that,when the VO_(2) is in insulating state,the device is a transmission polarization converter.The cross-linear polarization conversion can be realized in a broadband of0.70 THz,and the polarization conversion rate(PCR)is higher than 99%.Under thermal stimulus,the VO_(2) changes from insulating state to metallic state,and the device is a reflective polarization converter.The linear-to-circular polarization conversion can be successfully realized in a broadband of 0.50 THz,and the PCR is higher than 88%.
基金supported in part by National Science Foundation(NSF)
文摘We propose the design of anisotropic metamaterials with cascading meta-atoms.Each meta-atom array behaves as an impedance-tuned interface and dramatically modifies the complex reflection and transmission coefficients.By engineering the frequency-dependent impedances,the reflection phase difference along the two axes of anisotropic metamaterials approximates to a constant in a wide range.We numerically demonstrate the proposed anisotropic metamaterials can accomplish achromatic polarization transformation from 0.5 THz to 3.1 THz.The polarization conversion ratio is higher than 80%,which exhibits excellent agreements with the theoretical calculation.Such design is scalable to other bands and can provide helpful guidance in broadband devices design.
文摘In this paper, we propose a three-layered chiral metamaterial (CMM) that exhibits an asymmetric transmission effect for linearly polarized waves along forwardly and backwardly propagating in the microwave region, which not only realizes the asymmetric transmission effect of multi-frequency points for linearly polarized wave in microwave band, but also breaks through the limitation of single transformation from linear polarization to linear polarization. Numerical simulation results indicate that incident wave for linearly polarized waves will be converted and transmitted as a circularly polarized wave along the forward direction at 8.31 GHz. Moreover, the asymmetric transmission (AT) parameter Δ achieves 0.8 around 12 GHz, proving the existence of strong polarization conversion and diode-like function. The proposed CMM shows great potential applications in high performance linear polarization convertor and isolator in microwave frequency.
文摘In this paper,we propose an ultrabroadband chiral metasurface(CMS)composed of S-shaped resonator structures situated between two twisted subwavelength gratings and dielectric substrate.This innovative structure enables ultrabroadband and high-efficiency linear polarization(LP)conversion,as well as asymmetric transmission(AT)effect in the microwave region.The enhanced interference effect of the Fabry-Perot-like resonance cavity greatly expands the bandwidth and efficiency of LP conversion and AT effect.Through numerical simulations,it has been revealed that the cross-polarization transmission coefficients for normal forward(-z)and backward(+z)incidence exceed 0.8 in the frequency range of 4.13 to 17.34 GHz,accompanied by a polarization conversion ratio of over 99%.Furthermore,our microwave experimental results validate the consistency among simulation,theory,and measurement.Additionally,we elucidate the distinct characteristics of ultrabroadband LP conversion and significant AT effect through analysis of polarization azimuth rotation and ellipticity angles,total transmittance,AT coefficient,and electric field distribution.The proposed CMS structure shows excellent polarization conversion properties via AT effect and has potential applications in areas such as radar,remote sensing,and satellite communication.
基金supported by the National Natural Science Foundation of China (Nos. 62005143, 61831012, and 61971242)the Natural Science Foundation of Tianjin (No. 19JCYBJC16600)the Young Elite Scientists Sponsorship Program by Tianjin (No. TJSQNTJ-2017-12)
文摘We experimentally investigate the linear polarization conversion for terahertz(THz)waves in liquid crystal(LC)integrated metamaterials,which consist of an LC layer sandwiched by two orthogonally arranged sub-wavelength metal gratings.A Fabry-Perot-like cavity is well constructed by the front and rear gratings,and it shows a strong local resonance mechanism,which greatly enhances the polarization conversion efficiency.Most importantly,the Fabry-Perot-like resonance can be actively tuned by modulating the refractive index of the middle LC layer under the external field.As a result,the integrated metamaterial achieves multi-band tunable linear polarization conversion.
基金This work was supported by the National Natural Science Foundation of China(Nos.61675147,61735010,and 91838301)National Key Research and Development Program of China(No.2017YFA0700202).
文摘Phase-modulated metasurfaces that can implement the independent manipulation of co-and cross-polarized output waves under circularly polarized[CP]incidence have been proposed.With this,we introduce one particular metasurface composed of meta-atoms with a phase difference of 2π/3 to generate specific elliptically polarized waves under various polarized incidences.Furthermore,a metasurface composed of these above meta-atoms and the meta-atoms with a phase difference of π/3 arranged in a certain rule can realize polarization conversion function between linearly polarized and CP states.The designs shed new light on multifarious optical devices and may further promote the development of metasurface polarization optics.
基金supported by the National Natural Science Foundation of China(Nos.61531010,61270011,91438118,and 61501094)the National Key Basic Research Program of China(No.2014CB339806)
文摘In this Letter, we demonstrate a linear polarization conversion of transmitted terahertz wave with double-layer meta-grating surfaces, which integrated the frequency selectivity of a split ring resonator metasurface and the polarization selectivity of a metallic grating surface. Since the double-layer can reduce the loss, and the Fabry- Perot like resonant effect between the two layers can improve the conversion efficiency, this converter can rotate the incident y-polarized terahertz wave into an x-polarized transmitted wave with relatively low loss and high efficiency. Experimental results show that an average conversion efficiency exceeding 75% from 0.25 to 0.65 THz with the highest efficiency of 90% at 0.43 THz with onlv -2 dB loss has been achieved.
基金Project supported by the National Youth Foundation of China(Grant Nos.11904200 and 11704219)the National Natural Science Foundation of China(Grant No.11774053)+3 种基金the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20190726)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(Grant No.18KJD140004)NJUPT-SF(Grant No.NY218099)the Opening Project of the Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology(Grant No.hxkj2019007).
文摘This study proposes a bi-layer windmill-shaped metamaterial that consists of resonators, with similar shapes, on both sides of a dielectric substrate. In this study, the second layer is rotated clockwise around the substrate normal at 90°and thereafter flipped in the first layer. Due to the introduction of a windmill-like shape, the resonant structures result in new resonant modes and thus can achieve multi-band high-efficiency cross-polarization conversions and asymmetric transmissions(ATs) for a linearly polarized incident plane wave with a maximum asymmetric parameter of 0.72. Depending on the geometric parameters of our windmill-shaped structures, the AT effects can be flexibly modulated in a broad multiband from 160 THz to 400 THz, which has not been reported in previous studies. These outstanding AT effects provide potential applications in optical diodes, polarization control switches, and other nano-devices.
基金Project supported by the National Natural Science Foundation of China(Grant No.11304002)the Natural Science Foundation of Education Bureau of Anhui Province,China(Grant No.KJ2013A136)the Natural Science Foundation of Anhui Province,China(Grant No.1208085MA07)
文摘A three-dimensional chiral metamaterial with four-fold rotational symmetry is designed, and its optical properties are investigated by numerical simulations. The results show that this chiral metamaterial has the following features:high polarization conversion, perfect circular dichroism, and asymmetric transmission of circularly polarized light. A comparison of the results of chiral metamaterials without and with weak coupling between the constituent nanostructures enables us to confirm that the optical properties of our proposed nanostructure are closely related to the coupling between the single nanoparticles. This means that the coupling between nanoparticles can enhance the polarization conversion, circular dichroism, and asymmetric transmission. Due to the excellent optical properties, our metamaterial might have potential applications in the development of future multi-functional optical devices.
基金fnancial support from the National Key Research and Development Program of China(No.2022YFA1203502)the National Natural Science Foundation of China(Grant No.U2230114).
文摘Polarization,a fundamental behavior of electromagnetic waves,holds immense potential across diverse domains such as environmental monitoring,biomedicine,and ocean exploration.However,achieving efcient modulation of terahertz waves with wide operational bandwidth poses signifcant challenges.Here,we introduce an all-silicon polarization converter designed specifcally to operate in the terahertz range of the electromagnetic spectrum.Simulation results demonstrate that the average conversion efciency of cross-linear waves exceeds 80%across a wide frequency range spanning from 1.00 to 2.32 THz,with the highest conversion efciency peaking at an impressive 99.97%.Additionally,our proposed structure facilitates linear-to-circular polarization conversion with an ellipticity of 1 at 0.85 THz.Furthermore,by rotating the crossshaped microstructure,active control over arbitrary polarization states can be achieved.To summarize,the proposed structure ofers remarkable fexibility and ease of integration,providing a reliable and practical solution for achieving broadband and efcient polarization conversion of terahertz waves.